[Transposition of flexor pollicis brevis muscle for reconstruction of opposition function of the thumb: anatomical study and clinical application].

Anatomical study was performed on 20 cadaveric hands and the results showed that M. flexor pollicis brevis overlap the M. abductor pollicis brevis for about half of its width at their origins and the overlapping reduced to about 1/3 of the width at the muscle belly level. The M. flexor pollicis brevis chiefly inserts on the palmar aspect of the base of proximal phalanges. The M. abductor pollicis brevis primarily inserts to the radial side of MP joints, the M. flexor pollicis brevis is entirely innervated by the deep branch of the ulnar nerve. In order to increase the angle bettween longitudinal force lines of these two muscles for 7-9 degrees, the authors transfered the insertion of the M. flexor pollicis brevis to the radial side of the metacarpal-phalangeal joint, so that it gives this muscle the function of opposition. Eight patients had been treated and followed up on average for 12 months. All had fine functional results. This new methodis effective, least traumatizing and does not need transposition of another tendon.